OFFSET
0,6
COMMENTS
Number of partitions of n into squarefree parts > 1 (A144338).
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..5000
Joerg Arndt, Matters Computational (The Fxtbook), section 16.4.3 "Partitions into square-free parts", pp.351-352
Eric Weisstein's World of Mathematics, Squarefree
FORMULA
G.f.: Product_{k>=2} 1/(1 - mu(k)^2*x^k).
EXAMPLE
G.f. = 1 + x^2 + x^3 + x^4 + 2*x^5 + 3*x^6 + 3*x^7 + 4*x^8 + 5*x^9 + 7*x^10 + ...
a(9) = 5 because we have [7, 2], [6, 3], [5, 2, 2], [3, 3, 3] and [3, 2, 2, 2].
MAPLE
with(numtheory): seq(coeff(series(mul(1/(1-mobius(k)^2*x^k), k=2..n), x, n+1), x, n), n=0..60); # Muniru A Asiru, Jul 30 2018
MATHEMATICA
nmax = 65; CoefficientList[Series[Product[1/(1 - MoebiusMu[k]^2 x^k), {k, 2, nmax}], {x, 0, nmax}], x]
PROG
(PARI) {a(n) = if(n < 0, 0, polcoeff( 1 / prod(k=2, n, 1 - issquarefree(k)*x^k + x*O(x^n)), n))}; /* Michael Somos, Dec 26 2016 */
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Dec 26 2016
STATUS
approved